Starter unit

ABSTRACT

A starter unit comprising: an input and an output; a starter element, configured as a hydrodynamic component comprising a drive element that can be coupled to the input in a rotationally fixed manner and a driven element that can be coupled to the output. A free wheel mechanism is located between the driven element of the starter element and the output.

BACKGROUND OF THE INVENTION

The invention relates to a multifunctional unit, particularly a starterunit for use in change-speed gearboxes, and particularly automatic andautomated change-speed gearboxes, and it further relates to achange-speed gearbox, in particular an automated change-speed gearboxand to a vehicle with a change-speed gearbox.

Gearboxes for use in vehicles, in particular commercial vehicles, in theform of change-speed gearboxes or automated change-speed gearboxes areknown in a large number of different embodiments. The starting processis usually realized using a coupling device in the form of a frictionclutch or a hydrodynamic converter. However, use of a friction clutch asa starter element caused problems during operation, characterized byincreased slip over a longer time period. This applies especially to thestarting process. Due to the enormous thermal loading, the couplingdevice is then subjected to increased wear. In order to keep this wearas low as possible, appropriate demands are placed on the frictionlining used. Furthermore, the appearance of wear causes low service lifefor the starter element.

The disadvantage of using starter elements in the form of hydrodynamicconverters consists of the high costs for the hydrodynamic part and therequirement to provide a clutch mechanism.

An embodiment of a physical gearbox unit with a starter element in theform of a turbocoupling is known from German publication DE 196 50 339A1. At least two operating states are obtainable, namely a firstoperating state for transmission of power in at least one gear stage anda second operating state for braking. Both functions are realized usinga hydrodynamic coupling. This comprises a pump wheel and a turbinewheel, which together form a toroidal working area. The function of ahydrodynamic retarder is obtained by the function of the stator bladewheel, either by fixing with respect to a stationary gearbox component,to the pump wheel and the function of the rotor blade wheel to theturbine wheel, or the assignment of the function of the stator bladewheel to the turbine wheel by fixing the turbine wheel with respect tothe stationary gearbox components and the function of the rotor bladewheel to the pump wheel. In both cases, the blade wheel, which takesover the function of the rotor blade wheel, is coupled to the gearboxoutput shaft by means of the mechanical gearbox component. At the sametime, the turbocoupling is connected to the drive shaft or themechanical gearbox component of the physical gearbox unit such that, inorder to realize the first operating state, the turbine wheel can beconnected to the mechanical gearbox component and the pump wheel to thegearbox input shaft, while, to realize the second operating mode, i.e.braking, one of the two blade wheels is fixed. For this purpose, meansfor fixing and decoupling from the drive train are assigned to thehydrodynamic coupling, in particular to a blade wheel. This embodimentallows particularly compact physical gearbox unit to be formed, as aseparate braking element can be dispensed with. However, it has thedisadvantage for automatic change-speed gearboxes, in which the engineor turbine experiences a considerable change of speed during thegear-shifting process, during which the speed of the turbine wheel hasto be synchronized. However, when used in an automated change-speedgearboxes, a separate clutch mechanism must be provided in order toguarantee reliable interruption of the power flow during gear-shiftingprocesses.

SUMMARY OF THE INVENTION

The object of the invention is therefore to improve a starter unit foruse in change-speed gearbox components, to make it suitable for use inautomated change-speed gearboxes in drive systems, while avoiding theabove disadvantages. In particular, in doing so, a starting process thatis as free from wear as possible is realized, regardless of the durationof the state of increased slip. At the same time, the starter unititself should have low design and control technology effort and beeasily integrated into the drive system or into a power transmissionunit, for example in the form of a physical gearbox unit, whereby theever increasing requirements for a low overall length should be takeninto account. A further aspect of the invention comprises enablinginterruption of the power flow during the gear-shifting process.

According to the invention, a multifunctional unit, in particular astarter unit, comprises a starter element in the form of a hydrodynamiccomponent with at least one primary blade wheel and one secondary bladewheel, i.e. in the form of a hydrodynamic coupling or a hydrodynamicspeed/torque converter. The starter unit has an input and an output. Thestarter element to the unit, i.e. the hydrodynamic component, has adrive side and a driven side. The driven side of the starter element,i.e. of the hydrodynamic coupling, is connected to the output of themultifunctional or starter unit. A free wheel mechanism is providedbetween the secondary blade wheel, which is the turbine wheel whendesigned as a hydrodynamic coupling and as a converter, i.e. between thedriven element of the starter element, and the output of the starterelement. The free wheel mechanism, as a directional coupling,essentially allows two following functional states:

1. If the speed on the drive side of the starter element, i.e. theturbine wheel, is the same as that on the output of the multifunctionalunit, torque is transmitted from the turbine wheel to the output of themultifunctional unit.

2. If the speed of the turbine wheel, i.e. the driven element of thestarter element, is less than at the output of the starter unit, notorque is transmitted via the turbine wheel to the output and theturbine wheel free wheels.

The foregoing provides an almost wear-free starting process and has theadvantages that the hydrodynamic component does not have to be drainedduring the gear-shifting process that no additional clutch mechanism isrequired for interrupting the power. The decoupling of the input, whichas a rule forms the input shaft of the gearbox, from the subsequent gearstages is done solely by the free wheel mechanism, which thus safeguardsthe function of the synchronizing device in the change-speed gearbox.

In a further aspect of the invention, in addition to the starter elementbeing in the form of a hydrodynamic coupling, the starter unit comprisesa bypass clutch. These are both connected in parallel with one another.But they only act together during short or defined phases, to interruptthe power flow between the input and the output of the starter unit. Atthe same time, when the starter unit is used in automated change-speedgearboxes with a mechanical gearbox component downstream of the starterunit, this interruption capability can be achieved by the ability of thebypass clutch to switch while simultaneously draining the hydrodynamiccoupling or with the hydrodynamic coupling already drained, or, whenused in automated change-speed gearboxes with a mechanical gearboxcomponent or with a downstream or group gear-set by the draining of thehydrodynamic coupling when shifting between the first two lower gearstages. Advantageously, in this embodiment, the driven sides of thehydrodynamic coupling and the bypass clutch are coupled together in arotationally fixed manner by means of the free wheel mechanism. Thisarrangement has the advantage of only having to differentiate betweentwo states with regard to the transmission of power from the input ofthe multifunctional element to the output. The transmission of powertakes place either purely mechanically via the bypass clutch orhydrodynamically via the hydrodynamic component. In doing so, optimumuse can be made of the advantages of hydrodynamic power transmission forcertain driving conditions by means of the appropriate control. Thisapplies especially to the starting process, which can take placecompletely free of wear, and a complete bypassing of the hydrodynamiccoupling and its associated slip being realized under all other drivingconditions. Above a certain state of slip, which is dependent on thedesign of the hydrodynamic coupling, the bypass takes place by way of acoupling between the pump and the turbine wheel by means of a mechanicalbypass clutch. The drive power is transmitted to the output from a drivemachine, which can be coupled to the multifunctional unit, in particularto the input, with only small losses due to the mechanical transmissionsystems and the required auxiliary power. As the connection between thedrive machine and the driven element generally should be separated foruse in change-speed gearboxes, in particular synchronized change-speedgearboxes, when shifting between two gear stages, this task is assignedto the bypass clutch. This also applies analogously for the embodimentof the starter element as a hydrodynamic speed/torque converter.

At the same time, the rotationally fixed connection between the drivensides of the hydrodynamic component, in particular of the hydrodynamiccoupling or of the hydrodynamic converter after the free wheelmechanism, and the bypass clutch can be made in a releasable orunreleasable manner with regard to the fitting. In the first case, theconnection itself can be made in a flush and/or positively lockedmanner. In the second case, the connection can be realized, for example,by adhesive bonding or by designing the turbine wheel of theturbocoupling and the driven element of the bypass clutch as an integralcomponent—in the form of the clutch output disk of the bypass clutchwhen designed as a mechanical clutch with a multiple disk construction.The firm choice of the type of connection depends on the requirements ofthe application.

The bypass clutch is designed as a mechanical friction clutch,preferably with a multiple disk construction and preferably running wet.

Preferably, the hydrodynamic coupling, bypass clutch and free wheelmechanism components are integrated into a common housing. The bypassclutch preferably turns together in the operating medium of thehydrodynamic coupling or the hydrodynamic converter. At the same time,the commonly usable housing can be formed by

1. the housing of the hydrodynamic component, in particular thehydrodynamic coupling or the hydrodynamic converter, or

2. a separate housing, or

3. the housing of connecting elements, for example of a drive machine orof the gearbox.

In the last case, for example, it is conceivable to extend the housingeither solely of the drive machine, which can be coupled to the starterunit, or of the physical gearbox unit, which can be coupled to thestarter unit, or of both of the elements connected to the starter unit.

A starter unit according to the invention may be made very small andthus only has a small effect on the overall length when integrated intoa physical gearbox unit, in particular an automated change-speedgearbox. The constructional unit comprised of the hydrodynamic couplingor converter, bypass clutch and free wheel mechanism can be offered andsupplied by the trade as a pre-fitted modular component. Integrationinto a connecting unit then takes place in a positively locked and/orflush manner, for example by fitting the modular component to an inputshaft of the connecting element, in particular of a physical gearboxunit, or by a shaft to collar connection between the output of thestarter unit and the input of the connecting unit, whereby the inputshaft of the connecting unit can simultaneously form the output shaft ofthe starter unit in the assembled state.

When the bypass clutch is a mechanical clutch with a disk constructionin the form of a wet multiple disk clutch, there are a large number ofpossibilities for realizing the wet running of the multiple disks. Thisis preferably realized in a simple manner by simultaneously using theoperating medium, which is situated outside the working area of thehydrodynamic coupling, as a lubricant for the bypass clutch. As a rule,this is the operating medium, which collects in the operating mediumsump of the coupling housing or in a coupling tray or a storage chamber.In this case, additional sealing measures between the hydrodynamiccoupling and the bypass clutch can be dispensed with, and the bypassclutch can easily be integrated into the housing of the hydrodynamiccoupling. This embodiment enables design of a wear-free starter unit,which is particularly compact with regard to construction andfunctionality. These comments can also be applied to the converter.

In a further aspect of the invention, providing a device for optionallyfixing the turbine wheel enables operating the hydrodynamic couplingsimultaneously as a fully functional hydrodynamic retarder and thusenables producing a wear-free braking device. A separate hydrodynamicbraking device, which is used especially in commercial vehicles, can bedispensed with. Ventilation losses of the retarder are very low incomparison with the conventional retarder. The device for fixing orcoupling the turbine wheel to the housing, in the simplest case, isdesigned as a braking device, preferably with a disk construction. Thisacts on the driven element of the hydrodynamic coupling, i.e. on theturbine wheel. The connection of the braking element to the turbinewheel takes place between the turbine wheel and the free wheelmechanism. In a particularly advantageous manner, the vehicle can beprevented from rolling backward on inclines when the gear is engaged andthe braking element is closed.

Essentially, there are the two possibilities stated below with regard tothe spatial arrangement of the individual components of the hydrodynamiccoupling viewed in the axial direction from the input of themultifunctional unit to the output of the multifunctional unit:

1. Arrangement of the pump wheel of the hydrodynamic coupling betweenthe bypass clutch and the turbine wheel of the hydrodynamic coupling;

2. Arrangement of the turbine wheel of the hydrodynamic coupling betweenthe bypass clutch and the pump wheel of the hydrodynamic coupling.

In a further aspect of the invention, as an additional component in thestarter unit, a device for damping oscillations, in particular atorsional oscillation damper is integrated within this starter unit. Thetorsional oscillation damper can be functionally assigned either to thedrive side, as a particularly advantageous embodiment, or to the drivenside. With regard to the spatial arrangement, it is possible todifferentiate between the arrangement of the torsional oscillationdamper when viewed in its fitted position

a) spatially before the hydrodynamic coupling and before the bypassclutch, or

b) spatially before the hydrodynamic coupling and after the bypassclutch, or

c) spatially after the hydrodynamic coupling.

The combination of a hydrodynamic coupling or a hydrodynamic converter,a bypass clutch and, possibly, in addition a torsional oscillationdamper, and the integration into a modular component, provides thepossibility of creating a multifunctional drive component with a lowoverall space requirement. In doing so, these elements can be integratedinto a common housing. It is possible for the modular component to beoffered independently as a saleable component. At the same time, thehousing of the hydrodynamic coupling can be used as a common housing.

Other features and advantages of the present invention will becomeapparent from the following description of the invention which refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the invention are described in thefollowing text with reference to Figures:

FIG. 1 illustrates in a schematically greatly simplified representationan embodiment of the invention of a multifunctional unit, in particulara starter unit with starter element in the form of a hydrodynamiccoupling and a bypass clutch and a free wheel mechanism;

FIG. 2 illustrates in a schematically greatly simplified representationa functional improvement of an embodiment according to FIG. 1, thestarter element being suitable for transmitting torque or for producinga braking torque;

FIGS. 3 a and 3 b illustrate embodiments of the spatial arrangement ofthe individual elements of the hydrodynamic component for embodimentsaccording to FIG. 1 and FIG. 2;

FIG. 4 illustrates, by way of example, the individual functional statesof the starter units according to FIGS. 1 to 3 with reference to atable;

FIGS. 5 a and 5 b illustrate configurations according to FIGS. 1 and 2with the starter element designed as a hydrodynamic converter;

FIGS. 6 a and 6 b illustrate by way of example improvements of starterunits according to FIGS. 1 and 2 with an additional torsionaloscillation damper;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 is a schematic simplified representation of the basicconstruction of a starter unit 1 according to the invention, comprisinga starter element 2. The starter unit 1 comprises a hydrodynamiccomponent 18 in the form of a hydrodynamic coupling 3 and a bypassclutch 4. The hydrodynamic coupling 3 and the bypass clutch 4 areconnected in parallel. The hydrodynamic coupling 3 comprises at leastone primary wheel acting as a pump wheel 5 and a secondary wheel actingas a turbine wheel 6, which together form a toroidal working area 7. Thebypass clutch 4 can be designed in one of many ways, but preferably inthe form of a disk clutch, in particular a multiple disk clutch. Thiscomprises a clutch input disk 9 and a clutch output disk 10, which canbe brought into at least indirect active frictional contact with oneanother, i.e. either directly or via further disk-shaped intermediateelements, which form frictional pairs with one another. Furthermore, thestarter unit 1 comprises a drive element or input E, which can be atleast indirectly coupled to a drive machine not shown, and a drivenelement, which can be coupled at least indirectly to the driven elementin the drive system and which is also described as output A. Thedescriptions input and output refer here to the direction of power flowin traction mode when viewed from the drive machine to the drivenelement. The input E and the output A are, for example, designed in theform of solid or hollow shafts, which in each case can be coupled to theappropriate connecting elements—drive machine or gear stages—in thecustomary manner. Another known coupling between input and pump wheeltakes place via flex plates, which are rotationally stiff in thecircumferential direction and flexible in the axial direction. Whenviewed in this direction of power flow, the hydrodynamic coupling 3 asstarter element 2 likewise comprises a drive element 11 and a drivenelement 12. Here, the drive element 11 is formed by the pump wheel 5 oran element which is coupled to the wheel 5 in a rotationally fixedmanner, while the driven element 12 is formed by the turbine wheel 6. Atthe same time, the clutch output disk 10 and the driven element 12 canbe connected to the output A of the starter unit 1. However, accordingto the invention, a free wheel mechanism F is provided between theturbine wheel 6 or the driven element 12 of the hydrodynamic coupling 3and the output A. This produces a starter unit 1 which, in change-speedgearboxes, achieves positive effects both with the starting process andwith clutching processes. In particular, excessive wear in thesynchronizing devices during gear shifts can be reduced and comfort canthus be maintained or improved.

The table in FIG. 4 shows individual functional states of bypass clutch4, hydrodynamic coupling 3, the free wheel mechanism F and, in the caseof an embodiment according to FIG. 2, the additional braking device 13.

As a rule, the starter unit 1 according to the invention is coupled in adrive train to a speed or torque converter, i.e. a gearbox, or, withappropriate gear stages, forms a physical gearbox unit. Preferably, thestarter unit 1 is a constituent part of a physical gearbox unit so thatthe output A is coupled to the input of further speed/torque conversionunits. Automated change-speed gearboxes, are usually formed bymechanical transmission stages. Here, the whole gear unit including thestarter unit 1 and downstream speed/torque conversion units has theinput E of the starter unit as an input shaft. To enable a gear shift ina change-speed gearbox unit, the gearbox input shaft, which is formed bythe input E of the starter unit 1, must be free from torque anddecoupled from additional masses. Otherwise, there is a risk that thesynchronizing elements and/or claws of the gear-shifting elements of thephysical gearbox unit, in particular of the transmission stagesdownstream of the starter unit, would not be able to withstand the gearshift or would be considerably loaded and therefore would wear. To carryout a gear shift, both the drive machine and the turbine wheel 6 of thehydrodynamic coupling 8 must, in doing so, be decoupled from the gearboxinput shaft, which is formed by the input E or coupled to this in arotationally fixed manner. At the same time, the drive machine ismechanically decoupled with the bypass clutch 4 open. The decoupling ofthe turbine wheel 6 of the hydrodynamic coupling 3 is achieved by thefree wheel mechanism F, which for this task must free wheel. For thispurpose, the speed n_(T) of the turbine wheel 6 must be reduced to lessthan the speed of the output A. This occurs here either by reducing thespeed n₁ of the drive machine, as, when the hydrodynamic coupling 3 isfull, the speed of the turbine wheel 6 is reduced by the pump wheel 5,which runs at a reduced speed of the drive machine or a speedcorrespondingly proportional to it, which is applied to the input E ofthe starter element, or, according to an embodiment according to FIG. 2,an additional braking device 13 is provided, which acts on turbine wheel6 and effects a reduction in the speed n_(T) of the turbine wheel 6.

When making a gear shift, which characterizes shifting up, the speed atthe input E after shifting up is reduced by a certain stage step. Inthis case, the speed of the turbine wheel n_(T) must be further reducedto less than this connecting speed, i.e. the target speed of the drivemachine in the gear to be selected and thus the speed applied to input Eor one proportional to this speed applied to the input E, so that thefree wheel mechanism F free wheels and the gear-shifting process is madepossible.

FIG. 2 illustrates an advantageous improvement of an embodiment for astarter unit 1.2 according to FIG. 1, wherein the same references areused for the same elements. In this embodiment, the hydrodynamiccomponent 18.2 acts as a hydrodynamic coupling 3.2 in the startingprocess and, by exchanging the functions of the individual blade wheelsof the primary wheel 5.2 and secondary wheel 6.2, as a hydrodynamicretarder 19.2. An additional braking device 13, preferably a diskbraking device with a multiple disk construction, is coupled to thedriven element 12 of the hydrodynamic component before the free wheelmechanism F. To this end, the braking device 13 comprises at least afirst fixed disk 14, which is preferably arranged on the housing 15,which is only shown schematically here, and a second disk element 16,which can be brought into at least indirect active contact with thefixed disk 14, i.e. either directly or via further disk elementsconnected in between. The second disk element 16 is coupled in arotationally fixed manner to the driven element 12, particularly theturbine wheel 6. At least two operating states are realized with thehydrodynamic component 18.2—a first operating state for the transmissionof power, which in particular has an effect during the starting processand which describes the function of a hydrodynamic coupling 3.2, and asecond operating state for braking. The realization of the function ofthe hydrodynamic retarder 19.2 takes place by the assignment of thefunction of the stator blade wheel, by fixing with respect to thestationary gearbox components, in particular the housing 15, to thesecondary blade wheel, i.e. to the turbine wheel which operates 6.2 whenfunctioning as a hydrodynamic coupling 3.2. At the same time, thefunction of the rotor blade wheel is taken over by the primary bladewheel 5.2, which, when functioning as a hydrodynamic coupling 3.2, alsoacts as the pump wheel. There is an optimum possibility of fixing thesecondary blade wheel 6.2 and supporting it on the housing 15 due to thefree wheel mechanism F. Furthermore, this embodiment enables amultifunctional unit to be created for the realization of differentfunctions, i.e. in particular the starting process, the wear-freecoupling process and braking process when integrated into a change-speedgearbox.

At the same time, the state table shown in FIG. 4 illustrates, by way ofexample, for the embodiments according to FIG. 1 and FIG. 2 and,correspondingly transferred, also for the embodiments according to FIGS.3 a and 3 b, the individual functional states and switching variationsfor the appropriate elements of the starter units 1, 1.2, 1.3 a and 1.3b. In the neutral position or for engaging the first gear stage or thereverse gear, the bypass clutch 4, 4.2, 4.3, 4.3 b is open while thehydrodynamic component 18, 18.2, 18.3 a or 18.3 b respectively isdrained. A ventilation torque is produced by means of the primary bladewheel 5, 5.2, 5.3 a, 5.3 b by coupling to the input E of the starterunit 1, 1.2, 1.3 a, 1.3 b. The speed n_(secondary) applied to thesecondary blade wheel 6, 6.2, 6.3 a or 6.3 b respectively, whichcorresponds to the turbine wheel speed n_(T) of the hydrodynamiccomponent 18, 18.2, 18.3 a or 18.3 b respectively, at the same timecorresponds to the input speed at the input of the gear stages coupledto the starter unit 1. In this case, a so-called ventilation torque istransmitted by the air current enclosed in the toroidal working area 7due to circulation.

The starting process is characterized by the transmission of power bythe hydrodynamic component, in particular the coupling 3, 3.3 a or, inthe case of embodiments according to FIGS. 2 and 3 b, by means of thefirst operating mode of the hydrodynamic component 18.2 or 18.3 brespectively. In this case, the bypass clutch 4, 4.2, 4.3 a, 4.3 b isopen and the hydrodynamic coupling 3, 3.2, 3.3 a, 3.3 b is fully orpartially filled. At the same time, the operating medium in the toroidalworking area, which is being circulated due to the rotation of theprimary blade wheel, transmits a torque to the secondary blade wheel 6,6.2, 6.3 a or 6.3 b respectively. The speed of the primary blade wheel5, 5.2, 5.3 a or 5.3 b respectively essentially corresponds to that ofthe secondary blade wheel 6, 6.2, 6.3 a or 6.3 b respectively takinginto account the slip, i.e. n_(T)=n₂, which corresponds to the speed atthe input of the downstream gear stage, i.e. the speed (n_(A)) at theoutput A of the starter unit 1.

In the drive operating mode, i.e. in the second operating state, wherebytraction operation as well as overrun operation is included, as a rule,the power transmission is purely mechanical via the bypass clutch 4,4.2, 4.3 a or 4.2 respectively. This is closed. In this state, thehydrodynamic component 18, 18.2, 18.3 a or 18.3 b respectively is notinvolved in the transmission of power. In this case, the component caneither be drained, partially filled or completely filled. Thisparticularly plays a part if braking by means of the hydrodynamiccomponent is to be carried out during the normal driving process, i.e.in traction mode or overrun mode, as is conceivable in the embodimentaccording to FIG. 2 or 3 b. For this purpose, the hydrodynamic component18.2 or 18.3 b respectively is preferably completely drained, asotherwise a jolt would occur when engaging the braking device due to therapidly developing braking torque. When the signal for producing adesired braking torque is present, the braking device, which is in theform of the turbine brake, is closed and the toroidal working area isfilled with operating medium according to the desired torque. At thesame time, during the driving process, the speed of the turbine wheeln_(T) is less than that of the change-speed gearbox input shaft. Thesecondary blade wheel 6, 6.2, 6.3 a or 6.3 b respectively, which acts asthe turbine wheel, free wheels.

When shifting a gear, which characterizes shifting up, the mechanicalcoupling between the gearbox input, i.e. for example input E of thestarter unit 1, 1.2, 1.3 a or 1.3 b respectively, and the output A ofthe starter unit is interrupted. The hydrodynamic component 18, 18.2,18.3 a or 18.3 b respectively is empty, partially filled or iscompletely full. The speed of the drive machine n₁ coupled to the inputE is reduced and the speed at the secondary blade wheel 6, 6.2, 6.3 a or6.3 b respectively is less than that at the output n_(A) (or n₂, i.e.the input of the gear stages). The secondary blade wheel 6, 6.2, 6.3 aor 6.3 b respectively free wheels. In doing so, with an embodimentaccording to FIG. 2 (or Figure 6.3 or 6.3 b respectively), the brakingdevice 13 can be opened, or closed in order to brake the secondary bladewheel.

When shifting a gear, which characterizes shifting down to a lower gear,the bypass clutch 4, 4.2, 4.3 a, 4.3 b or 4.2 respectively is open. Thehydrodynamic component 18, 18.2, 18.3 a or 18.3 b respectively in theform of the hydrodynamic coupling 3, 3.2, 3.3 a, 3.3 b can be empty,partially filled or completely full. In this case too, the speed n_(T)of the secondary blade wheel 6, 6.3 a, 6.3 b, 6.2 is less than the speedat the output n_(A) of the starter unit 1, 1.2, 1.3 a or 1.3 brespectively. The secondary blade wheel 6, 6.2, 6.3 a or 6.3 brespectively is free from any coupling with the output A.

In order to realize braking, with an embodiment according to FIG. 2 andFIG. 3 b, the braking device 13 is closed and, moreover, the bypassclutch 4.2, 4.3 b. The hydrodynamic component 18.2 or 18.3 brespectively must be full or at least partially filled. Due to the freewheel mechanism F, the secondary blade wheel 6.2 or 6.3 b respectivelyrotates at a lower speed n_(T) or at zero speed (stationary secondaryblade wheel) than the output A of the starter unit 1.2 or 1.3 brespectively.

Different gear stage combinations are possible with the individualgear-shifting processes, including shifting up or shifting down, in thecase of the embodiments shown, all combinations that are theoreticallypossible. This makes it possible to shift from a first starting geareither to a next higher or next lower gear stage or, by skipping one ormore gear stages, to a higher or lower gear.

FIGS. 3 a and 3 b illustrate embodiments according to FIGS. 1 and 2, inwhich, however, the spatial arrangement in the axial direction viewedfrom the input E to the output A of the starter unit 1.3 a or 1.3 brespectively of the individual blade wheels i.e., the primary bladewheel 5.3 a or 5.3 b respectively and secondary blade wheel 6.3 a or 6.3b respectively of the hydrodynamic components 18.3 a, 18.3 b, iseffected in such a way that the primary blade wheel 5.3 a or 5.3 brespectively is arranged between the bypass clutch 4.3 a or 4.3 brespectively and the secondary blade wheel 6.3 a or 6.3 b respectively.

FIGS. 5 a and 5 b illustrate an embodiment with hydrodynamic component18.5 a and 18.5 b in the form of a hydrodynamic speed/torque converter20.5 a and 20.5 b respectively. The basic construction of the starterunits 1.5 a and 1.5 b corresponds to that described in FIGS. 1 and 2,and only the hydrodynamic component 18 has been replaced by ahydrodynamic speed/torque converter 20.5 a, 20.5 b. The same referencesare therefore used for the same elements. The embodiments shownillustrate examples. Embodiments with another spatial arrangement of theindividual elements of the converter with respect to the spatialposition of the bypass clutch are also conceivable.

FIGS. 6 a and 6 b illustrate, with reference to embodiments of starterunits 1.6 a and 1.6 b according to the invention according to FIG. 1 or2, the integration of a further component in the form of a device 17 aand 17 b respectively for damping oscillations, preferably a torsionaloscillation damper. Functionally, this is either assigned to the driveside, i.e. the input E of the starter unit 1.6 a, as shown in FIG. 6 a,or this embodiment is particularly advantageous. Another possibility,according to the FIG. 6 b, comprises functionally assigning the devicefor damping oscillations 17 b to the driven side, i.e. to the output Aof the starter unit 1.6 b. It is possible with regard to the spatialarrangement to differentiate between the arrangement of the device fordamping oscillations 17 b when viewed in its fitted position

-   -   a) spatially before the hydrodynamic coupling 3.6 a and before        the bypass clutch 4.6 a, or    -   b) spatially before the hydrodynamic coupling 3.6 b and after        the bypass clutch 4.6 b, or    -   c) spatially after the hydrodynamic coupling 3.6.    -   a) is shown in FIGS. 6 a and b) is shown in FIG. 6 b.

The arrangements shown in FIGS. 1 to 6 are examples and do not limit theprotective scope of the application. Other embodiments, in particularthe combination of the starter unit with additional elements, areconceivable and lie within the discretion of the person skilled in theart.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

1. A starter unit for a driven arrangement, the starter unit comprising:a rotation input to the starter unit and a rotation output from thestarter unit; a hydrodynamic coupling, the hydrodynamic couplingincluding first and second rotatable fluid coupling elements; a driveelement coupled in a rotationally fixed manner to the input, a separatedriven element, drivable by the drive element and which is coupled tothe output, wherein: the first and second rotatable fluid couplingelements are respectively a primary wheel of the hydrodynamic couplingconnected to the drive element and a secondary wheel of the hydrodynamiccoupling connected to the driven element, the primary wheel and thesecondary wheel being the sole mechanism for coupling torque between thedrive element and the driven element; and the wheels of the hydrodynamiccoupling define a toroidal working area with a cross section in the formof two full circles, and which is at least partially fillable to avarying extent for varying torque between the primary and the secondarywheels; a free wheel mechanism between the driven element and theoutput; a selectively lockable bypass clutch arranged between the inputand the output, wherein: the bypass clutch is connected in parallel withthe hydrodynamic coupling between the input and the output; the clutchis operable to lock the input to the output and to release the lockingof the input and the output; and the clutch is selectively lockable andreleaseable independently of the filling and emptying of the toroidalworking area; and a device providing fixed support of and braking of thesecondary wheel.
 2. The starter unit of claim 1, further comprising adevice for damping oscillations and disposed between the input and thebypass clutch.
 3. The starter unit of claim 1, further comprising adevice for damping oscillations and disposed between the bypass clutchand the output.
 4. The starting unit of claim 1, wherein the primarywheel is arranged axially between the input and the output and betweenthe bypass clutch and the secondary wheel.
 5. The starting unit of claim1, further comprising a housing wherein the device for providing fixedsupport is supported.
 6. The starting unit of claim 5, wherein thedevice for braking is arranged on the driven element of the hydrodynamiccoupling and disposed before the free wheel mechanism.
 7. The startingunit of claim 5, wherein the device comprises a friction brake and thefriction brake comprises at least one element bearing a friction surfaceand fixed to the housing and comprises a second element bearing afriction surface and coupled in a rotationally fixed manner to thedriven element of the hydrodynamic coupling.